1. Field of the Invention
The present invention relates to a work-sheet retaining apparatus for retaining a work sheet on a support plate.
2. Related Art Statement
There is known a work-sheet retaining device which retains a work sheet on a support plate such that an excessive outer peripheral portion of the work sheet which overflows the upper surface of the support plate is folded and inserted between the lower surface of the support plate and the upper surface of a table disposed below the support plate. A sewing machine incorporating the retaining device is disclosed in U.S. Pat. No. 4,821,659. The disclosed sewing machine automatically (a) folds an excessive outer peripheral portion of a "pocket" material or cutting as a first work sheet, (b) superposes the pocket cutting on a second work sheet such as a front-body cutting of a garment, and (c) attaches the pocket to the front body by forming stitches along the folded peripheral edge of the pocket.
The operation of the above sewing machine is detailed below, by reference to FIGS. 6(a) to 6(f) which show respective steps (a) to (f) carried out by a sewing system 8 in accordance with the present invention. Those steps are commonly effected by the prior sewing machine and the invention sewing system.
In Step (a) of FIG. 6(a), a pocket cutting, P, is placed on a support plate 24 disposed above a table plate 14 of the sewing machine, and a work-sheet folding frame 28 is pressed on the support plate 24. Thus, an excessive outer peripheral portion, P1, of the pocket cutting P which is overflowing the upper surface of the support plate 24 is folded downward by the folding frame 28 along the outer peripheral edge of the support plate 24.
In Step (b) of FIG. 6(b), a plurality of folding members 35 are actuated by respective air cylinders 33 supported on a common folding-member holder 32, so that the folding members 35 are moved toward the lower surface of the support plate 24. Consequently, the peripheral portion P1 of the pocket cutting P is folded onto the lower surface of the support plate 24.
In Step (c) of FIG. 6(c), the work-sheet folding frame 28 and the folding-member holder 32 are moved downward as a unit onto a front-body cutting, W, provided on the table plate 14.
In Step (d) of FIG. 6(d), the air cylinders 33 are driven to move the folding members 35 away from beneath the support plate 24.
In Step (e) of FIG. 6(e), the work-sheet folding frame 28 and the folding-member holder 32 are moved upward as a unit.
In Step (f) of FIG. 6(f), while the pocket cutting P is pressed on the front-body cutting W by a presser plate 19, the support plate 24 is removed from the cutting P. Subsequently, the pocket cutting P whose peripheral portion P1 is folded back on the front-body cutting W is sewn along the folded peripheral edge thereof by a stitch-forming device. Thus, the pocket P is attached to the front body W.
The prior sewing machine, however, suffers from the problem that the work sheet P retained on the support plate 24 may move out of position due to vibration produced in Steps (c) to (e), in particular, Step (e) where neither the folding frame 28 nor the presser plate 19 is pressed on the pocket cutting P.
U.S. Pat. No. 4,813,362 or No. 4,819,572 discloses another work-sheeting retaining device including a support plate on which a work sheet is placed; a table plate which has holes formed through thickness thereof, like holes 83 of the table plate 14 shown in FIGS. 6(a) to 6(f); and (B) a vacuum device which sucks air from above the table plate through the holes thereof. In this device, the support plate is retained by air suction on the table plate, with an excessive outer peripheral portion of the work sheet being pinched between the support and table plates. Thus, the work sheet is more or less prevented from moving out of position on the support plate.
The second prior retaining device ensures that the outer peripheral portion of the work sheet is pinched with increased force between the support and table plates. However, an inner portion of the work sheet supported on the upper surface of the support plate is free of the force to fix it in position. Thus, the prior device suffers from the problem that the work sheet may move out of position and accordingly wrinkle on the support plate.